Within the field of packaging technology use is often made of consumer packages configured for single use. Such packaging container may be manufactured from a laminated packaging material comprising a paper or cardboard core and outer protecting layers or coatings of a plastic such as polyethylene. The plastic layers provide protects the core from moisture emanating from the product inside the packaging container or from the outside of the packaging container. The packaging laminate may also comprise further layers adapted to provide a barrier against passage of gases such as oxygen, or a barrier against passage of light. One such further layer may be a metallic foil arranged between the core and at least one of the moisture barriers. Aluminium foil is commonly used. Optionally the core may be replaced by a non-cellulose material. It is worth stressing that the area of packaging laminate is a field of research continuously developing and since the present disclosure does not relate to the packaging laminate as such it will not be discussed any further. The application of the present disclosure should not be limited to the example given, but rather the invention may be used in the processing of any packaging laminate.
A packaging container made from a packaging laminate is a well known product to most people. In a modern processing line such a packaging container is manufactured and filled in a packaging line or filling line, were packaging laminate from a reel or in the form of individual blanks are fed to a machine in one end thereof and filled containers made from the packaging laminate exits in the other end. In the filling line the packaging laminate has been formed, filled and sealed, to make a long story short. As was the case for the packaging laminate, the field of filling lines is a vast area on its own, and not the prime issue for the present disclosure. Still, in one example, a web of packaging material is fed to a filling machine. In the filling machine the web is formed into a tube and its longitudinal edges are sealed to one another, forming a hollow cylinder having a longitudinal seal. The hollow cylinder is gradually filled with pourable product and by performing transversal sealing below a product level in the tube a chain of pillow-shaped, filled, packaging containers is formed. The chain may then be severed into individual packaging containers which are formed into, e.g. packaging containers having a parallelepiped shape. Examples of such a container is Tetra Brik. If every other transversal seal is shifted 90° the renowned container Tetra Classic may be formed. In other concepts individual blanks—rather than a web of packaging material fed from a reel—are fed to the filling line. A magazine feeds the blanks one by one into the filling line, where each blank is folded into a packaging container which is sealed at one end. After the packaging container has been filled it is sealed and folded at its other end. Typical packaging containers within this concept is the Tetra Rex and the Tetra Top.
Moving closer to the field of the present invention; a laminated packaging material, or packaging laminate, of the type described above is manufactured in industrial scale from a web of paper or carton being formed into a roll. The web (i.e. the free end of the roll) is guided to a first processing station where one side thereof is provided with a repetitive décor or pattern of aesthetic or informative character, using a suitable printing technique of which there is a few. In the same processing station or in an adjacent processing station the web is provided with a likewise repetitive pattern of weakening lines. The purpose of the weakening lines, or crease lines, may be to facilitate folding of the packaging containers formed from the packaging material at a later stage. The décor and the pattern of crease lines should of course be in register with each other for every formed packaging container to have the same appearance.
In subsequent processing stations the web is provided with the barrier layers of plastic and/or foil.
The order of processing steps may vary; in some concepts the printing is performed after the barrier layers have been arranged, just to mention one example.
At this stage in the process the web has a width corresponding to several packaging containers, and this web is divided longitudinally into “one-package width webs”, or sub webs, which are rolled into rolls for later use in a filling line. In the following the word “web” will mostly refer to these sub-webs, but as a general principle the technique to be disclosed may as well be applied on the original larger web, or on a different web altogether.
During the entire process the quality of the packaging laminate is monitored, such that physical or cosmetic errors may be accounted for. Each serious flaw is registered and in a separate process the web of packaging material is “doctored”, meaning that a defect segment of the web is removed after which the formed free ends are spliced together for formation of a continuous web. In this way there is a reduced risk of problems later on in a filling line using the web of packaging material.
A doctoring line used for the above purpose, of a conventional design, has a first horizontal rotatable shaft at one end thereof and a corresponding second horizontal rotatable shaft at the other end thereof. The web of packaging material is arranged on a reel on the rotatable shaft at the first end, is guided through the doctoring line and wound up on a reel arranged on the second rotatable shaft. In the doctoring line there is equipment arranged to locate detected errors and to remove segments of the web and splice the formed free ends together. The web is wound from the first reel to the second reel, and when an error is located the web is stopped and a doctoring sequence is commenced, after which the winding starts over. For one single roll of packaging laminate the doctoring sequence may be initiated repeatedly, and in each doctoring sequence a segment of the web will be wasted.
A doctoring line is often a complex construction of rolls and reels, as well as nips and brakes for the web to pass through, and when a new roll of packaging material is arranged on the first reel a leading end of the web needs to be thread through the doctoring line.
One section of the doctoring line is a “pull and brake” arrangement. One objective of a pull and brake arrangement is to master the web transport, by controlling the web speed. An existing pull and brake arrangement is shown in FIG. 8. The arrangement comprises four rollers, three of which have fixed rotational axes. The first and the second rollers are arranged on the same height, while the second roller is shifted downwards on a centreline between the first and the third roller. Notably and obviously up/down, left/right etc are given as example only, in order to facilitate understanding of one prior art arrangement. The web is thread over the first roller, under the second roller and over the third roller, essentially being formed as a U. Below the second roller a fourth roller is arranged. The fourth roller is movable in the up/down direction, and it is used to clamp the web of packaging material between the second roller and the fourth roller with a variable force. Through variation of the force the tension in the web of packaging material may be controlled. Understandably, threading of such a pull and brake arrangement is a complex procedure, and since there is a need to perform that operation at least once per roll of packaging material there is a considerable effort put into it.
One purpose of the present disclosure is to provide an improved pull and brake arrangement facilitating threading of a doctoring line, or at least a pull and brake arrangement thereof. An effect of the novel arrangement, according to some embodiments thereof, is that the handling of waste formed in the doctoring procedure is significantly simplified.